text: For a launch of a space vehicle from the ground, dynamic pressure is:
  * zero at lift-off, when the air density ρ is high but the vehicles speed v' = 0;
  * zero outside the atmosphere, where the speed v is high, but the air density ρ = 0;
  * always non-negative, given the quantities involved.
  During the launch, the vehicle speed increases but the air density decreases as the vehicle rises. Therefore, by Rolle's theorem, there is a point where the dynamic pressure is maximal.
  In other words, before reaching max , the dynamic pressure increase due to increasing velocity is greater than the dynamic pressure decrease due to decreasing air density such that the net dynamic pressure (opposing kinetic energy) acting on the craft continues to increase. After passing max , the opposite is true. The net dynamic pressure acting against the craft decreases faster as the air density decreases with altitude than it increases from increasing velocity, ultimately reaching 0 when the air density becomes zero.
  This value is significant, since it is one of the constraints that determines the structural load that the vehicle must bear. For many vehicles, if launched at full throttle, the aerodynamic forces would be higher than what they can withstand. For this reason, they are often throttled down before approaching max  and back up afterwards, so as to reduce the speed and hence the maximum dynamic pressure encountered along the flight.